\subsubsection{Windowing}
\textit{Windowing} is the extraction of an audio signal into a single frame.  The purpose of of windowing is to improve the frequency-domain presentation. In order to perform windowing, one must multiply the signal frame with the \textit{window function} point by point \cite{audio.signals1}. Windowing is required in short-time signal processing, a process where a signal is cut into small frames and processed one at a time.

According to \cite{audioEffect_defintion}, audio effects can be classified into the following sets of categories:

\begin{itemize}
\item \textbf{Basic Filtering} - Lowpass, Highpass filter, Equaliser
\item \textbf{Time Varying Filters} - Wah-wah, Phaser
\item \textbf{Delays} - Flanger, Chorus, Echo
\item \textbf{Modulators} - Ring modulation, Tremolo, Vibrato
\item \textbf{Non-linear Processing} - Compression, Limiters, Distortion,
Exciters/Enhancers
\item \textbf{Spacial Effects} - Panning, Reverb, Surround Sound
\end{itemize}


\subsubsection{Ring Modulation}
Ring modulation is an audio effect that can be achieved by multiplying two input signals, the output being the difference or sum of the two signals - thus resulting in frequencies that are usually inharmonic \cite{ringmodulcir}. As the name suggests, the physical component is formed by a ring formation of diodes. The analogue output generates a more authentic sound compared to digital, although more difficult to achieve; while from the digital perspective simply requires one to multiply the inputs. Among one of the common uses of the ring modulation is to create tuned instruments that produce inharmonic frequencies (e.g. bells or chimes), furthermore allowing to achieve a greater spectrum of timbre compared to any other method of audio manipulation \cite{ringmodul}. 

\begin{figure}[htbp]
\centering
\includegraphics[width=0.7\textwidth]{images/TheoryDesign/ringmodulpic}
\caption{A visual representation of a ring modulator- Sin 1 and Sin 2 being the two inputs and Wave A being the output - \ref{fig:ringmodulpic}}
\label{fig:ringmodulpic}
\end{figure}

\subsubsection{Noise Gate}
When utilizing the "gater" effect or the noise gate, a commonly used audio effect, there is a threshold level which allows frequencies exceeding the threshold to pass, otherwise sharply attenuating frequencies which are below that level. This effect can be used for effectively suppressing undesired noise while allowing the desired parts of the signal to pass. One can use the gater effect to remove background noise, crosstalk from other signal sources, and low-level hum, among other uses. \cite{gater}

\begin{figure}[htbp]
\centering
\includegraphics[width=0.5\textwidth]{images/TheoryDesign/gateeffect.png}
\caption{How a noise gate works. The threshold effectively sharply attenuates signals below, while leaving higher values unaffected}
\label{fig:gater}
\end{figure}